WhatsApp Server and Privacy - WhatsApp Security

When
you install WhatsApp messenger, all your contacts will be uploaded to
the WhatsApp server. It takes every contacts regardless of the fact
whether the person in the address book is a Whatsapp user or not.
This enables to quickly update the
contacts list in
the messenger.

This
is a major WhatsApp security concern as in the case if the server is
hacked, the hacker will
get access to all
the contacts stored in their
server, even though this information is stored in encrypted format and will not
store any other details associated with the phone number.

Privacy
of Messages or Files Sent Through WhatsApp

WhatsApp
does not copy nor store the messages sent through its messaging
system. Even if the recipient is not connected to the internet and
haven't received the message, the undelivered messages will be kept
in WhatsApp servers and may be stored in those servers for up to 30
days. After this period of time, messages are deleted; and from that
moment on messages will only be stored in the emitter’s and the
recipient’s devices. But they may store the date and time of
delivered messages, as well as the mobile phone numbers of the
devices involved.

WhatsApp
states that files that are sent using WhatsApp service are kept in
their servers only for a short period of time. After this time they
are finally eliminated according to their “general retention
policies”.

Another
major WhatsApp privacy concern is that a user does not need to send a
friend request to send messages to another user, anyone having phone
number could send message to any other person. However, users can
block numbers on WhatsApp.